1. Field of the Invention
The invention relates to the field of video compression. More specifically, the invention relates to object based motion compensation.
2. Background of the Invention
A video signal contains image repetition redundancies that are not essential to its apparent quality. Removal of these redundancies in the video signal significantly lowers the number of bits required to synthesize the video signal. Usually, a motion compensation technique is used to remove these redundancies. A motion compensated prediction method is applied to the current and a previous or a future image (frame) to generate motion vectors. Motion vectors represent the difference in position between the current frame, or a part of current frame, and the displaced reference frame, or a part of the reference frame.
Different methods are used to perform motion compensation. One motion compensation method computes motion compensation vectors for each of the fixed size blocks comprising an image. In this case, the motion compensation vector represents the difference in position between the block from the current frame and the displaced block from the reference frame.
Motion compensation is also performed based on objects of an image. Objects are formed from an image based on current frame information (for example, luminance and/or color changes). Objects are also formed based on wavelet filtering without taking into account object movements. These methods for motion compensation are inefficient because neither method accounts for movement.
Many convention motion compensation methods have a limited search range for finding object and block displacements. Moreover, search complexity grows substantially as the search range increases.